Inter-outer telephone system



May 4, 1937. R. VARLEY' 2,079,089

7 I INTER-OUTER TELEPHONE SYSTEM v Filed Aug. 21, 1935 s shetsesheet 1 INVENTOR.

ATTORNEYS.

May 4, 1937. R. VARLE Y 2,079,089

' INTER-OUTER TELEPHONE SY STEM Filed Aug. 21, 1955 5 Sheets-Sheet? I INVENTOR.

flaw/hep M42440.

[VITA/55$ B I ATTCRNEYJ.

May 4, 1937. R. VARLEY INTER-OUTER TELEPHONE SYSTEM Filed Aug. 21, 1935 s sheets-sh et s lllllllllllld Paw/42y A24 E WITNESS.

ATTORNEY-5.

Patented May 4, 1937 UNITED STATES 2,679,089 v a mraa-ou'rsa ramrnonn srs'rm Richard Varley, St. George, N. Y., assignor to Inter-Outer Telephone Corporation,

Dover,

-Del.,a corporation of Delaware Application August 2 iessjseriai No. 31,104

- 29 Claims. (01. 179-1) This invention relates to improvements in systems of'telephonic communication and has spe cial reference to acoustically-coupledinter-outer telephone systems of the general type set forth in my copending application Serial No. 733,824, flled July 5, 1934.

One of the objects of my present invention is to provide such an acoustically-coupled interouter telephone system, in which a public telephone system may be efl'ectively and efficiently connected in-acoustical relation to an entirely separate and electrically independent private .inter-omce telephone system, without in any way lnterferring with or modifying the normal operation of the public telephone system, while enabllng any branch station of the inter-office system to fully utilize the facilities and service of the public telephone system. 7

Another object of my invention is to simplify tion of such an acoustically-coupled inter-outer telephone system, and to extend the use and benefits ofthe public telephone system to a privately owned and operated inter-omce telephone system, while at the same time providing the inter-outer system with improved features of operation and control which are now unavailable in public telephone systems.

A further object of my invention is to provide 3 improved facilitiesfor readily effecting an efflcient acousticaltcoupllng between the outer public telephone system and the inter-omce system, and, without disturbing or affecting the property of the public telephone system, to utilize the subscriber's publlc'telephone set-in such a way that the mere act of picking up the French telephone instrument from its supporting base will perform certain novel and useful functions which are advantageous and desirable to thetelephone user, and. 4" will also initiate and expedite the operationof I certain component parts of the inter-oiiice system, whereby a prompt and eificiently operative acoustical connection may be established be tween the outer and the inter-ofllce systems.

, These and other objects of my invention, and

' features thereof by means of which they are accomplished, will become apparent from the folpartially in section, of a portion of an acoustical 5 couplingdevice employed in myinvention;

and improve the circuit connections and opera- Fig. 3-is a fragmentary view, partially in plan I and partially in section, of a portionof' the coupling device shown in Figure 2 and taken along the section line III-III thereof; Fig. 4 is a diagrammatic. view of a modified and improved telephone system embodying my invention and Fig. 5 is a diagrammatic view illustrating a of certainjeatures of my operators station or, through the agency of an acoustical coupling device between the interofiice system and the usual subscriber's telephone of a public telephone system, is enabled to communicate with any outside party having a subscribers telephone.

In accordance with this form of my invention,

provision is made for automatically operating a signal and a timing device and also supplying energy to an electronic amplifier associated with the receiving circuit of the interofllce system as soon as the public telephone instrument is picked up by the operator in answering a call. v

Another feature of the invention is the automatic setting up of independently operable and controllable receiving and transmitting circuits in the inter-office system as soon as the receiver at the branch station is picked up for-use.

A furtherfeature of the invention resides in providing an acoustical coupling device with which the French telephone instrument of the public telephone system is placedin acoustical relation for inter-outer communication with control means which is so located as to necessitate its operation by the operator before a complete and efficient acoustical coupling can be effected, and which operates in conjunction vwith-auxiliary circuits and devices to prepare for a subsequent and automatic signal to the operator when the telephone conversation has terminated and the called party has hung up his receiver. The operator being thus warned, restores the. telephone instrument to-its cradle andcuts off the 'power from the electric amplifier and the firstmentioned signal and timing device.

To accomplish these ends, myinvention comprises a main or operators station 0 and a plurality of branch stations A and B, which stations may be located at separate points, as in difierent having a French-style telephone instrument F constituting a part of the public telephone system. Also disposed adjacent thereto is an acoustical coupling and control device C by means of which the electrically independent outer and inter telephone systems may be connected'acoustically and their operation controlled, in accordance with my inventidn.

The subscribers telephone set T is provided as usual with a base 2, a dial-operating mechanism 4 and a cradle 6 upon which the French-style telephone instrument F rests when not in use. The instrument F is of well-known construction and embodies a receiver 8 and a transmitter l0 disposed in fixed spaced relation at the respective ends of a hand grip I2.

I In order to provide a signal or warning to the operator at such times as telephone instrument F is in use and out of its cradle, the base 2 is positioned upon a movable or floating platform I4 of a sub-base 16, which platform rests-upon a plurality of supporting springs l8 carried within the sub-base member. A stationary spring contact 20 is fixedly mounted upon an insulating block 22 secured to the sub-base I 6 and in cooperative relation with said spring contact is another spring contact 24 which is mounted on an insulating block 26 secured to the underside of the floating platform l4.

When the telephone instrument F rests in its cradle 6, the weight of the entire telephone set T is sufilcient to depress the springs l8 and hold the spring contacts 28 and 24 out of engagement. But when the telephone instrument F is moved from its cradle for use, the weight of the base 2 is insuflicient to hold down the platform and the springs l8 raise the platform and telephone base 2, while at the same time bringing the movable spring contact 24 into cooperative engagement with the contact 20. An electrical connection is thereby established from the source of power, marked Power, through power supply wire 30, spring contacts 24 and 28, conductor 34 and thence through a visible or audible signal device 36, such as a lamp or buzzer, which by means of conductors 38 and 39 is-connected to the other supply wire 40 from the source of power.

It is sometimes desirable and convenient for the telephone user, particularly when calling a long distance station, to be kept informed as to the length of time of his call,and for this purpose, a timing device 42 is employed which is connected in parallel with the signal device 38 by means of conductors 34 and 46. This timing device conveniently comprises an electric-clock mechanism of the usual type and preferably embodies an alternating current self-starting synchronous motor which rotates an indicator needle 48 in the usual manner. Thus, the operator is visibly and progressively informed as to the length of time of long distance calls. Of course, the signal device and the timing device are maintained in operation until the telephone instrument F is restored to its cradle.

The acoustical coupling and control device'C is located adjacent the public telephone set T so that the French telephone instrument F may be temporarily hung or placed in acoustical operative relation with the coupling device 0. This coupling device C comprises a'box-like casing or cabinet 50, parts of which are shown more in de tail in Figs. 2 and 3, to which reference is made. This cabinet is provided with an inclined front panel 82 having suitably spaced openings 54 and. 58 which are spaced in vertical relation so as to register with the receiver 8 and transmitter I0 of the French phone F when placed in acoustical operative position over said openings and supported in position by an outwardly extending semi-circular supporting flange member 58 which is suitably secured to the front inclined panel 52.

In order to pick up the sound emanating from the receiver 8 of the French telephone F, there is mounted within the cabinet 50 immediately back of the opening 54 and in registry therewith, a microphone which is preferably of the wellknown two-button type, although any other suitable type of microphone may be employed. Adjacent the inner end of the panel opening 56 and in registry therewith is mounted a loud speaker 62 of any suitable and well-known construction.

Intermediate the openings 54 and 56 in the panel 52 is an outwardly projecting member 64 suitably attached to the panel proper. and slidably positioned therein is a switch actuating rod 66 having at its outer end a handle or head 68.

The inner end or said rod is connected to a switch mechanism 10 which may be of any well-known construction and preferably constitutes a fourpole double-throw snap switch shown in outline in Fig. 3. the, operating lever 12 of which is pivotally connected at 14 to the inner end of the actuating rod 58.

Without describing in detail the construction of the snap switch, it will be understood that this type of switch embodies a'spring which rapidly throws or snaps the movable contact members into or out oi electrical engagement when the operating lever is moved past its dead-center position. Such type of switch not only accomplishes a rapid make-and-break of the electric circuits associated therewith, but, when used in conjunction with the push rod 66, serves to accentuate or hold it in either its inner or outer position, thus requiring a definite push or pull by the operator to eiTect the operation of the switch associated therewith.

In the schematic diagram of Fig. 1, the control switch 10 is merely shown diagrammatically and comprises a plurality of spring contacts 16, I8, 80 and 82 which are mounted in an insulating block 84 and out of contact one with the other, although a button 88 of insulating material is fixedly mounted on the spring contact 18 and is in physical engagement with the spring contact 80. However, when the actuating rod 66 is pushed inwardly by the operator, the inner end 88 thereof, which in Fig. 1 comprises insulating material, presses against the spring contact l6 and brings the pairs of contacts 16 and 18 and also contacts 88 and 82 into electrical amplifier is typified by the RCA Victor Portable Sound Amplifier-Type P. (1-63 or theUniveraal operated on batteries.

Amplifier Assembly (0 watts) may be employed. While the particular amplifiers mentioned are adapted to be connected to an alternating current source of power, my invention may be car ried out with any type of amplifier, such, for

example, as those which are connected to a direct current source of power, or those which are All such amplifiers, regardless of their type, are provided with means 'ior regulating. or adjusting thedegree of amplification. This is a desirable adjunct in my system,- but since it is conventional with all types of amplifiers, it is typified in the drawings only by a simple adjusting knob 00 The cabinet 50 alsocontains a change-over switch 92 for shifting certain circuit connections of the system in accordance withcertain aspects of my invention. This change-over switch 92 may conveniently. take the form of a four-pole, double-throw switch having a plurality of contact arms 04, 95, 90 and I00 which are pivotally mounted at one end and pivotallv attached to an interconnecting insulating, bar I02. so that they may be moved in unison. Each of the contact arms above referred to is adapted to occupy two operative positions to cooperate with a plurality of stationary contacts I04, I06, I08. H0, H2, H0, H5 and H8. In the operative position shown in Fig. 1, contact arm 94 cooperates with contact I04, contact arm 90 with contact I08. contact arm 08 with contact H2, andcontact arm I00 with contact IIG. In the other operative position, contact arm 94 cooperates with contact I06, contact arm 95 with contact H0, contact arm 58 with contact H0, and contact arm I00 with contact H8.

For convenience in operating the change-over switch 92. the interconnecting bar I02 is provided with a handle H9 which projects throu h a slot in one of the side walls of the cabinet 50, where it is accessible to the operator for manipulation.

Also within the cabinet 50 are conveniently located auxiliary pieces of apparatus, such as buzzer I20, electromagnetically-operated switch I24, batteries I26 and I28 and certain necessary circuit connections for my system.

The branch'stations A and B are alike and for illustrative purposes each embod es a'walltype telephone extension, although any type of telephone may be used. As shown, each comprises a' casing I30 within which is disposed a transmitter H2 and an ear type receiver I34. The rece ver I34 is normally hung, when out of use. on the hooked end I38 of a hook lever I30 which is pivotally mounted at. I40, and the weight of the receiver is sumcient to hold the hook lever in its downward position against a stop I42 in opposition to the action of a co l spring I44. which raises the hook lever when the receiver has been removed therefrom. Immediately above an operating finger I46 of insulating material forming a part of the hook lever 138 is a control switch me hav n a plu ality of spring contacts I50. I52, I54. I56 and I58 which,

- tact I54 is provided with an extended end por tion I62 which is normally engaged. by an insulating button I64 secured to the lower spring from its hook lever I00, the finger I44 efiects anelectrical engagement between the spring contacts I00 and I52, and at the same time,

through the insulating button I 04, spring con tact I04 is raised and an electrical connection effected between the spring contacts I54, I50

.and I58, as shown at station B.

For-the purpose of enabling the operator to call any of the branch stations, a. suitable signal or buzzer system S is provided and, as shown, includes a battery I60 to which is connected a push-button I10 adjacent the operator's station and a plurality of buzzers I14, respectively located at branch stations A and B and adapted to be energized through the operator's push button I10, so that through an agreed-upon code, either one station or the other may be rung or called. Of course any type of signal system may be used.

The phonograph P is of a type generally known as a dictating machineand is located in a separate room or sound-proof compartment adjacent the operators station 0. Without describing the phonograph in detail, it will be understood that broadly it includes a driving motor I which serves to rotate a mandrel I82 upon which a wax recording cylinder I84 may be inserted in the I usual manner. A sound reproducer I 86 engages the recording cylinder and is fed lengthwise thereof as the cylinder rotates and, in so doing, reproduces upon the cylinder thevocal sounds which are transmitted through a flexible speaking tube I88 having a mouthpiece Itfiin acoustical operative relation with the open side of a contact I50; when the rebeiver I04 is removed I92, and for the purpose of picking up sound waves produced thereby is a microphone 8% preferably of the one-button type, although any suitable microphone may be used, and this microphone functions to pick up and transmit the sound waves or speech received thereby into electrical waves over a suitable. electric circuit.

The operation of the phonograph P may be remotely controlled by the main station operator through the agency of the usual Bowden'wire I in a well-known manner by means of which the usual clutch operating mechanism (not shown) of the phonograph may be operated by depressing the operating knob I98, as will be understood from common practice.

Having set forth the general construction and operation of several parts of the apparatus emp oyed in my system, and assuming the receivers I34 at both stat ons A and B to be hung upon their respective hook levers, the operation and circuit connections of the system will be described and my invention more fully explained;

Assuming the French-style telephone instrument F to beresting in its cradle 6 and that a call is received on the subscribers telephone set '1. the operator picks up the instrument F and determines that the party calling desires to speak with someone at branch station A. The operation is as follows:

Upon removing the telephone instrument F from its cradle 6. the decrease in weight of the telephone set T is such as to permit the springs I8 to raise the floating platform I4 with the telephone stand 2 thereon sufiiciently to cause the engagement of spring contacts and 24, and the consequent operation of the visible or audible signal 36 and also of the timing device 42 through 42 indicates the duration of time of the call.

In addition to eifecting the operationof the.

Signal device 36 and the timing device 42, the cooperative engagement of the contacts 20 and 24 also performs another important function. It immediately connects the electronic amplifier 80 to the source of power so as to promptly initiate the warming-up period thereof in order that it may be more quickly ready for service. This is accomplished through a circuit across the source of power which includes conductor 30, contacts 24 and 20, conductor 34 and conductor I91 to one of the terminals I99 of the amplifier 90 andfrom the other'terminal thereof through conductor 40 to the source of power.

As the operator answers the outside call and proceeds to locate the party desired, the amplifier, which has been connected to the source of power, gradually becomes heated to operative condition and is in readiness for use.

This feature of energizing the amplifier when the French telephone instrument is removed from its cradle, is also of special importance when I employ an amplifier of the battery-operated type, such as are now available, and as shown in connection with the modification set forth in Figure 5 of the drawings.

The operator having determined, for instance, that a party at branch station A is being called, signals station A, as by a single ring or buzz, through the agency of the push-button I10. When the party at branch station A removes the receiver I34 from the hook lever I36, the spring I44 raises said lever and, by so doing, effects the electrical engagement of the spring contacts I50,

I52, I54, I56 and I in the manner .previously' described. Thus, the one-way two-wire transstation 0 is completed and rendered operative through a circuit from oneside of the battery I26 through conductor 200, loud-speaker 62, conductor 202, conductor 204, transmitter I32, conducor 206, spring contacts I54 and I56, conductor 208 and conductor 2I0 to the other side of the battery I26. The party called is thus able to speak to the operator who receives the message through the loud-speaker 62.

In the meantime, the amplifier 90 has been heated up and becomes operative to intensify any electrical waves set up in response to speech in the microphone and transmitted to the amplifier through its input circuit 2I6. The output circuit of the amplifier 90 is thus rendered operative and includes conductor 2I6, contact arm 94 and contact I04 of change-over switch 82,

conductor 220, conductor 222, spring contacts I50 and I52 of control switch I39, receiver I34 at branch station A, conductor 224, conductor 226, contact I00 and contact arm 96 of the changeover switch 32 and conductor 226 to the other party called at branch station A that he has a call from the outside public telephone system.

It is pointed out that the operation of the system up to this point is typical of the manner of operation of my system when used for interofiice communication between any branch station and the main or operator's station.

Before proceeding with a description of the acoustical connection between the outer and the inter-telephone systems, an important control or signal feature of my invention should be understood. This involves an audible signal to the operator, after the party at branch station A has concluded his conversation and has hung up his receiver I34. In order to understand this feature, it is necessary to revert to the time when the receiver I34 at branch station A was first removed from its hook lever I38, since a part of the circuits of this control or signal feature is established at that time, inasmuch as the spring contacts I56 and I58 are then brought into engagement. This engagement completes a circuit from battery I26 through electromagnet 230 of the electromagnetically-operated switch I24, and thence through conductors 232 and 234, spring contacts I56 and I56 01 control switch I39, conductors 206 and 2! to the other side of the battery. The completion of this circuit energizes the electromagnet 230 which draws its armature 236 against the action of a spring 238 to separate switch contacts 240, one of which is mounted on the armature 236, to thereby open an auxiliary circuit in which the buzzer I20 is adapted to be connected. Under these conditions, the buzzer I20 is inoperative.

As soon as the party at station A is ready to receive the outside call, the operator depresses the actuating rod 66, thereby bringing contacts 16 and I6 of the control switch I0 into engagement, as already explained. This places energy from battery I26 on the stationary contact 240 of the switch I24 through conductors 242 and 244 and the intervening contacts I6 and 18. The movable contact 240 on the armature switch arm 236 is already connected to the battery I26 through the armature switch arm 236, buzzer I20 and conductor 245.

However, the buzzer I20 is still inoperative by reason of the fact that the electro-magnetically operated switch I24 is in open position because of the energization of its electromagnet 230, as already explained. While the buzzer I 20 is not now operative, the necessary connections have been established so that, as soon as the party at branch station A hangs up his receiver I34, the electromagnet 230 will become de-energized and the armature switch arm 236 actuated by the spring 236 to close the contacts 240. Thus, the buzzer I 20 will be connected across the battery I26 and becomes operative to warn the operator that the conversation has been terminated and that the French telephone instrument should be restored to its cradle.

To continue with the operation of the system, the operator, having depressed the actuating rod 66 and actuated the control switch 10, places the French telephone instrument F in the position shown in Figs. 1 and 2, with the receiver 0 thereof adjacent and in acoustical relation with the microphone 60 of the coupling device C and the transmitter I0 thereof in acoustical relation with the loud speaker 62 of the coupling device. With the telephone instrument F-so placed, it is supported by the semi-circular flange 58 over which the receiver 6 is hung. The hand grip I201 2'0 1 way receiving circuit which includes the -receiver that the telephone instrument F can not be placed in complete acoustical relation with the coupling ao'i'aose g the instrument rests against or is positioned ad-i ss g, for exmple h conversation b I jacent the actuating knob or button 60 of the actuating rod 86, which 'has'previously been pushed in by the operator to operate the control switch II. The actuating rod isso positioned device c until the actuating rod is, depressed and the control switch 10 closed. d h

An acoustical couplingbetween the subscribers -public telephone systernand the inter-.oflice sys'- tem having thus beenefiected, without electri-- -ca1ly interconnecting the systems or interfering in any way with the normal operation of the outside system, the conversatlon'proceeds infa normal manner, during which the outside-call is transmitted through the receiver 6 of'the teledevice C and thence through the two-wire one- I34 at branch station A.; On the other hand,

the conversation of the party at branch station A-is transmitted to the outside calling party the message is delivered acoustically to the usual transmitter l0 of the French telephone instru- '.ment. Of course, by utilizing the adjusting knob fill the operation of the amplifier 90 may be, regulated as desired;

Having completed the conversation, the'party at branch station A hangs up his receiver I34, thus disengaging all of the spring contacts of control switch I39 within the telephone set at station A and-interrupting or disconnecting both the transmitting and the receiving circuitS as well as the circuit through the electromagnet 230. Thereupon, the armature 236 thereof is moved by the spring 238 to close the contacts 240 and'energize the buzzer I20, thus signalling the operator that the conversation has been com pleted and that it is necessary to restore the French telephone instrument F to its normal position upon the cradle 6. v

In removing the telephone instrument'F from the acoustical coupling device C the operator also grasps the knob or-button 60 of theactuating rod. 66 and pulls it intoitsouter position, at which time the associated control switch I0 which is preferably of the snap switch type, operates to break the circuit of buzzer I by disengaging spring contacts I0 and I8. v 7

Of course, if the operator should neglect to pull out the actuating rod 66, the buzzer I20 would continue to operate until this is done. The operator then replaces the French telephone instrument F upon its cradle, at which time the added weight of the instrument depresses the floating platform I4 and thereby disengages the spring contacts 20 and 24 to cut 01? the supply of electrical energy to the amplifier 90, signal device 35, and timing device 42. The entire interouter system is thus restored to normal conditions and is ready for subsequent use.

As an adjunct to the system hereinbefore de-.-

' scribed, I hayeprovided the sound recording device or phonograph P already set forth, which may be utilized for the purpose'of making a fee- 'ordot any incoming message'should it be found desirable to do so,while still permittingthe party tween an outside calling station and a party'at branch station -A to be in progress and the cirwit-connections being as heretofore set forth,

- should .it become desirable torecord any message ductors 252: and 254.

"Before attempting to record an incoming message, the operator actuates the change-over switch 92 by means of its handle '9 to its other or recording position 'in which the contact arms 94, 96, 98 and I00 are moved into positions v a to engage thecontacts I06, III), H4 and H8. phone instrumentF and through the microphone Gland electronic amplifier 90 of the coupling- A to the loud-speaker I92 of the phonograph P,v while, at the same time," theauxiliary pick-up microphone I94" positioned adjacent the loud speaker. I92 is connected through battery I28 through the transmitter I32 of branch station A g -and thence through an independently operable 'tWO-IW'iI'B one-way transmitting circuit, which includes the loudspeaker 62, by means of whichv and powercontrol switch 10,150 the receiver I34 ,atbranch station A. r

j More specifically, the movement of the changeover switch 92 into its, other or recording position establishes a circ'uit'from the output side ofthe amplifier 90 through conductor 2I8, switch switch 'III,'conductor 262, contact arm 98 and contact 4 of the change-over switch 92, conductor 264, conductor 226, conductor 224,'re-

. ceiver I34, spring contacts I52 and I50 of "control switch I39, conductor 222, conductor 220,

conductor 266, contact [I8 and contact arm I00 of change-over switch 92, conductor 268, microphone I 94 associated with the phonograph P, and conductor 210 to the other side of the bat- 'tery.-. v I

The circuit just recited, including the battery 1 120, the pick-up microphone IM and thereceiver I34 of branch station A, serves to'acoustically receive a message from the loud speaker 3 I92 of the phonograph P and transmit it to the receiver of branch station A so. that the party talking thereon will be able to listen to the message from the outside system which is being recorded by the phonograph P. It will be noted that during the recording of outside messages v in the. manner just described, the receiving circult is transferred to the loud-speaker of the phonograph, but .is still independently operable from the transmitting circuit.

Having set upthe circuits just described for the purpose of recording outside messages, the actual reproduction thereof by the phonograph P. is initiated by the operator dep'ressingthe actuating knob I90 at the end of the Bowden wire I96 in order to'actuate the usual clutch-operating mechanism between the driving motor I80 and the phonograph proper.

0f course, with'the system described with respect to Fig. 1 of the drawings, it is possible ior any branch station to converse with themaln or operators station and also to be acoustically coupled to the subscribers outside telephone system.

Referring now to Fig. 4 of the drawings, a modified and improved system embodying my invention is illustrated diagrammatically, in which any branch station may converse with the operator's station and also may be acoustically coupled to the subscribers outside telephone.

This modified system is generally analogous in many respects to the system already described but embodies certain improved features. For instance, in addition to means for automatically energizing the electronic amplifier as soon as the French telephone instrument is removed from its cradle, my modified system also includes an auxiliary battery-operated transmitter associated with my acoustical coupling device, so that immediate communication with a branch station may be established before the amplifier reaches a proper operating condition. Also with this arrangement, it is unnecessary to energize the amplifier at all for inter-office communication.

Another operating feature is a simplified arrangement of the independently operable trans mitting and receiving circuits which utilize a common return instead of comprising two separate two-wire circuits, thus enabling the use of control switches of more simple construction at the branch stations, with correspondingly simpler circuit connections, while still permitting independent control of the respective circuits.

A further feature is an automatic lockout end signal system whereby whenever one of the branch stations is in operation it is impossible for any other branch station to cut in or be operably connected to the system. Other improvements will also be apparent as the description proceeds.

This modification of my invention also includes a buzzer and annunciator signal system of the so-called auto-call type, whereby any branch station may signal the operator and register an indication of such signal by means of an annunciator in the event that the operator is temporarily absent, and whereby the operator may selectively signal any branch station and through an annunciator located at each station indicate that such a call has been made in the event no one is present to answer the signal.

In the system of Fig. 4, there is shown an operator's station 0 and branch stations A, B, C. -At the operators station is a subscriber's outside telephone set T having a French phone F of the usual type and this subscriber's telephone set rests upon a sub-base (not shown) similar to that illustrated in Fig. 1. which is also provided with relatively movable spring contacts 20 and 24 which are adapted to make cooperative electrical engagement when the telephone instrument F is removed from its cradle. In Fig. 4, however, the engagement of the spring contacts 20 and 24' is utilized to connect a suitable electronic amplifier 90 with the'source of energy, marked Power, as soon as the telephone instrument F is removed from its cradle and, at the same time, a visible signal 36 is brought into action. A timing device, such as set forth in connection with Fig. 1, may also be employed, if desired. The power circuit of the amplifier 90, which is thus established, includes conductor 214, spring contacts 20' and 24, and conductor 216, while the other power connection to the amplifier comprises conductor 218. The signal device 36 is simultaneously connected across the source of power by means of conductor 280.

By immediately energizing the amplifier 90 when the telephone instrument F is removed from its cradle, the amplifier tubes are quickly subjected to heat and reach a suitable condition of operation before being called upon to function in the system.

Also located at the operator's station 0' is an acoustical coupling and control device C of which the amplifier 90' constitutes a part and which is generally similar to that described in connection with Fig. 1. This coupling device is shown only diagrammatically but it will be understood that it is of the same general construction as that already described and includes a similar micro: phone 60, a loud-speaker 62, a control switch I0, 9. switch-actuating rod 66, batteries I26 and 284, a signal device or buzzer I20, an electromagnetically operated switch I24, and an auxiliary transmitter or microphone 288.

The control switch 10' comprises a plurality of spring contacts 290, 292, 294, 296and 298 which are mounted on an insulating block 300 in such manner that spring contacts 294 and 296 are normally in engagement, while the other spring contacts 290, 292, and 298 are out of engagement and are, therefore, electrically inoperative. Spring contact 292 carries at its extended free end a button 302 of insulating material which is I adaptedto engage the extended free end of spring contact 296. When the'switch actuating rod 66 is pushed in, engagement is effected between spring contacts 290 and 292, while the electrical connection between spring contacts 294 and 296 is interrupted and, at the same time, an electrical engagement of spring contacts 296 and 298 is established.

The various branch stations A, B, C are similar in construction and a description of branch station A will be sufllcient. At branch station A is a telephone set which is shown for illustrative purposes as of the wall type, and which includes a transmitter I32 and a receiver I34 which normally hangs on a. hook lever I38 pivoted at I40 and held downwardly against a stop I42 by the weight of the receiver I34 when it is hung upon the hook lever. A spring I44 cooperates with a downwardly extending arm 304 of the hook lever to raise the hook lever whenever the receiver is removed therefrom. The hook lever I38 is also provided with an insulating finger I46 disposed beneath a control switch I39 comprising a spring contact 306 and a plurality of cooperating spring contacts 308, 3i 0 and 3I2, all of which are mounted on an insulating block 3I4. When the receiver I34 is in position on the hook lever I38, the spring contacts are out of engagement, but when the receiver is removed therefrom, the spring I44 raises the hook lever to cause the insulating finger I46 to engage the spring contact 306 and press it upwardly into electrical engagement with the spring contacts 308, 3I0 and 3I2. V

For the purpose of preventing the operation of other branch stations when one of the branch stations is being utilized, each of the hook levers I38 is provided with an upwardly extending segment 3I6 having a notch 3I8 therein into which latch 322 constitutes the armature of an electromagnet 324 and is normally held in its upward smaoao position against a stop ,by means, of a spring 828. When'the electromagnet is energized, the locking finger 320 of the armature 322 is pulled down into the notch 3I8 into locking engagement with the segment 3I6 to prevent the hook levefilfl from being raised, even though the receiver be removed therefrom.

Disposed above the armature-latch member 322 and in the path or movement thereot is a bellcrank lever 328 which is pivoted at ill, and its horizontal arm carries an adjustable weight 332,

while the extremity of its vertical arm carries a signal disk I. The bell-crank lever 32! constitutes a sort of semaphore signal and normally occupies a position such as shown in Fig. 4 with a depending finger 338 thereof resting upon the latch-armature 322. However, when'the electromagnet 324 is energized, and its armature 322 is pulled down into locking position, the bell-crank semaphore 328 rotates in a counterclockwise direction'by reason of the weight! and moves the signal disk 334 into registry with an opening or window 338 in thecasing (not shown) or the telephone wall set. If the disk an be painted red, for convenience, it will visibly indicate through the window. 338 ,that the inter-oillce system is already busy or in use. Any party desiring to use the branch station will, therefore, wait until the systein is clearf'or out oi use. course, in lieu of a semaphore signal, any other suitable visible or audible buzzer signal maybe employed. K

For the purpose of enabling the operator selectively signal any branch station and also for any branch station to signal the operator's sta' tion, a suitable buzzer or signal system S of the so-called auto-call type is employed, and asso ciated therewith are suitably located push buttons and annunciators, functioning in the usual manner to leave a visible indication of a call in the event that no one is present at the time the call is made. This buzzer or signal system S is common in the art and will be understood without deat the operators station, and which are operatively connected to a common buzzer 344.

Assuming the circuit connections to be as shown in Fig. 4, and that an outside call is received on the subscriber's telephone set T, the French telephone instrument F is removed from its cradle by the operator and'the call is answered. The decrease in weight of the telephone set T, by reason I of the removal of the instrument F, causes the source of power marked Power to be immediately connected through switch members 20 and 24 to the amplifier 90, while at the same time the signal device 36 is operated, all in the manner pre+ vicusly described in detail.

By energizing the amplifier 90' immediately upon removing the telephone instrument F" from its cradle, the amplifier tubes arepromptly subjected to heating current and are quickly brought i to operative condition, so thatthe amplifier will of the branch stations.

be in readiness for service by the time the desired party has been called to the proper branch sta- The operator having ascertained the party de* sired then depresses one of the push buttons, for instance, Illa, in the event that the desired party is located at station A, thereby signaling station A by means of the combined'buzzer and annunciator unitJ Ha. In responding to the signal, the party at station A lifts the receiverlfl' from its wall set and is at once enabled to talk with the operator through the transmitter I32, which, by reason of the operation of the control switch I39, is connected into circuit with battery I28 and the loud speaker 62' associatedwith the coupling device C at the operator's station. This transmitting circuit is established automatically as the-receiver III is removed from its libok lever, inasmuch as'the spring Ill then operates- I thus established includes battery I26, conductors 346,448, loud-speaker 62, conductors 350, 352, c

transmitter I22, conductor 3", spring contacts 306, 306, and 3H! 01 control switch I39 associated with branch station A, and thence through conductor 356 and conductor 358 to the other side of thebattery.

Simultaneously. an operatively independent receiving circuit, including the transmitter 288 at the operator's station-and the receiver I34 at station A, is established. This circuit includes battery l2i, conductor 316, conductor 380, transmitter 288, conductor 362 and spring contacts 294 and 28B of control switch 10 associated with the acoustical coupling device C. which contacts are the only ones of said control switch which are normally in engagement, the circuit being completed through conductor 384, conductor 3%, receiver I34 at station A, conductor 368, spring contacts 306 and 3III of control switch I39, and thence back to the battery through conductors 35B and 358.

Upon the completion of the local or inter ofilce transmitting and receiving circuits just recited,

, the party at branch station A and the operator may converse as desired, during which the party at station A will be advised of the call and in turn will advise the operator that he is ready to a to understand certain control features ofimy invention which are initiated at the time 'the receiver I34 at station A is removed from its hook lever. This feature has to do with automatic "lock out arrangement, by means of which all of the other branch stations are definitely latched in such a manner as to prevent their use while sta tion A is being used.

To accomplish this result the circuit arrangements are such that when the control switch I39 associated with branch station A is actuated into its closed position, upon the removal of the receiver I34, a circuit is established from battery I26 which includes the electromagnets 324 of all This circuit also includes the electromagnet of control switch I 24' at the operator's station. The circuit by which this is effected includes battery I26, conductor 346, con- 324,associated with the telephone set at station C, conductor 313, electromagnet 324 at station B', conductor 333, electromagnet 324 at station A, conductor 332, conductor 334, spring contacts 312, 333 and 3" of control switch I33 at station l5 3I3 of the respective segments 3I3, in locking engagement therewith, to thereby positively prevent the upward movement of the respective hook levers I33 in the event that the receivers I34 01 said stations should be removed therefrom. Of course, the latching armature 322 of station A is prevented from being pulled downwardly into the notch '3I3 associated with the segment 3I8 of its hook lever I33 by reason of the fact that upon the initial removal of the receiver I34 therefrom, the hook lever wasraised and the associated segment 3I3 rotated clockwise beneath the end of the latching finger 323 so that even though the electromagnet 324 at station A be energized.

it is impossible for its latch-armature 322 to be moved.

However, the other branch stations B and C are locked against use as already described, and, moreover, the semaphore signal devices of these other branch stations will operate, as already set forth, to visibly indicate at the openings or windows 333 of the respective wall sets that the system is "busy" for the time being. Therefore, any

party at these stations, noting that the busy" signal is set, will refrain from attempting to utilize the system imtil this visible signal indicates that the system is clear and ready for use.

At the same time that the automatic locking feature just described. is rendered operative, the electromagnet 314 of control switch I24 atthe operator's station is also energized, and this magnet attracts its armature 333 against the action of spring 333, thereby disengaging the cooperating contacts 333 of the electro magnetically operated switch I24, which contacts are in circuit with the warning buzzer I23. Thereby, the buzzer circuit is opened and the buzzer prevented from operating for the time being.

Reverting now to the acoustical coupling of the inter-oilice system with the outside system, after the party at station A has indicated that he is ready to receive the outside call, the operator then depresses the actuating rod 33' of the acoustical coupling device C to actuate the control switch 13' and placw the French telephone instrument F in positionupon said coupling device in the manner described in connection with Fig. 1, whereby the receiver 3' is in registry with and in acoustical relation to the microphone 60', while the transmitter I3 occupies a position in registry with and in acoustical relation to the loud speaker In so actuating the control switch 13', the normal engagement of spring contacts 294 and 233 is broken, while establishing engagement be- .tween spring contacts 233 and 232 and the spring contacts 233 and 233, as will be understood.

The interruption of the circuit through the transmitter 233 by reason of the disengagement of spring contacts 234 and 236 renders this transmitter and its receiving circuit, hereinbei'ore described, inoperative. However, by this time, the amplifier 93', which was connected to the source of power when the telephone instrument F was first removed from its cradle, will have now become heated up to full operative condition and 5 ready for use.

Concurrent with the interruption of the receiving circuit through the transmitter 233, another receiving circuit is set up from the output side of the amplifier which includes conductor 392, 10 spring contacts 233 and 233 of control switch Ill, conductor 334, conductor 333, receiver I34 at the station A, conductor 333, spring contacts 303 and 3") of control switch I33 and thence through conductors 333, 333 and conductor 334 to the other 6 side of the output circuit of the amplifier 30'. This receiving circuit is operatively independent of the transmitting circuit previously described, although these two operative circuits include a common return circuit. 'The arrangement how- 0 ever, is such that both circuits are independently controllable. The utilization of a' common circuit for both of the independently operable and independently controllable transmitting and receiving circuits materially simplifies the circuit 25 "connections and permits a correspondingly simpler construction of the control switches III and I33 Having eiiected an acoustical coupling between the subscribers telephone instrument F'of the 39 outside system and the inter-oflice system by means of the acoustical coupling device C in the manner described, and having established the independently operable transmitting and receiving circuits, as above set forth, the conversation 35 between the calling party on the outside system and the called party at station A may be carried on in the usual manner.

During the conversation the visible signal 36' at the operator's station 0' continuously indi- 40 cates that the conversation is in progress. Also, by reason of the look-out? arrangement, previously described, it is impossible for any of the other branch stations B and C to interfere with or break into the conversation. Moreover, the 45 semaphore signal devices associated with the branch stations B. and C visibly indicate that the system is'in use and is not available at these branch stations, until such-time as the conversation in progress has terminated. -50

Before describing the operation of the system after the conversation has been terminated, it is important to understand certain preparatory or intermediate functions of my system which are carried out at the time that the control switch 13' 55 of the. coupling device C is actuated by the operator through the actuating rod 66'. This has to do with preliminarily setting up suitable signal circuits which will later become operative when the receiver at the branch station A is hung up 00 at the conclusion of the conversation, and at which time the buzzer I20 will operate to warn the operator that as the conversation has terminated, the French telephone instrument F should be restored to its cradle on the public 65 telephone set.

In connection with this control feature it has already been explained that upon the removal of the receiver I34 at station A, electromagnet 314 of the electromagnetically operated switch 70 I24 in the acoustical coupling device 0 is energized to attract its armature 333 and thus separate the cooperating contact members 333 to thereby open a circuit including the buzzer 236. However, when the control switch III is actuated 75 G operated switch I24 which is located in the '386 and thence through conductor 400 to arma ture 386 and its associated contact 390 of the electromagnetically operated switch I24. This switch, being now in open position, by reason of the energization of electromagnet 314,.as already explained, prevents the operation of the buzzer I20, although the other cooperative switch mern for the operation as soon'as the conversation her 390 is connected by conductor 402 and conductor 358 with the other side of the battery.

The circuit of the warning buzzer I20 at the operators station 0' is thus placed in condition been completed and the receiver I34 at stationli A has been restored to its hook lever I38. When this is done, the weight of the receiver I34 moves hook lever I38 at station A to its downward position in opposition to the spring I44. Thereby, the control switch I39, associated with station A, is permitted to resume its normal open position, whereupon the receiving circuit and the Y transmitting circuit, together with the energizin'g circuit of the lock-out electromagnets 324, are interrupted, and by reason thereof all of said electro-magnets deenergized. This permits the latch-armatures 322 atbranchstations B and C to be retracted by their springs 326 out of locking engagement with the notched segments 3I6 of their associated hook levers. In this manner the telephone wall sets at branch stations B and C are released from their locked inoperative positions and restored to their normal condition in readiness for subsequent use.

Of course, the telephone wall set at station A is also ready for use, in view of the disengagement of segment 3I6 of its hook lever I38, which was .efiected at the time that the receiver I34 was again restored to said hook lever. Contemporary with the restoration of the several branch stations A, B and C to normal position, the associated semaphore signal disks 334 of stations 3 and C are returned to their "clear positionsas indicated in Fig. 4, by reason of the springs 326, through the agency of the latch-armatures 322 and the Weighted bell crank levers 328, upon which the signal disks 334 are mounted. The warning buzzer I20 at the operators station 0' is rendered operative when the control switch I39 of branch station A is opened upon the restoration of the receiver I34 to its hook lever, in view of the fact that the opening of the control circuit through the electromagnets 324 of the several branch stations also deenergizes electromagnet 314 of the electromagnetically acoustical coupling device C at the'operators station. As won as this electromagnet is deenergized its armature 386, which carries one of the cooperating contacts 390, is actuated by spring 388 to the position shown in the drawings in which the energizing circuit through the buzzer 236 and contacts 390 is closed.

Thereupon, the buzzer I20 becomes operative to give a warning signal to the operator that the conversation has terminated and the receiver I34 at station A had been hung up. This buzzer signal continues in operation until the French telephone instrument F is moved from acoustical relation with the acoustical coupling device C and the control switch restored to'its initial condition of operation by the operator pulling out the actuating rod 63' to thereby reestablish the initial circuit conditions under which the interoflice telephone system is again rendered operative for inter-office communication or for further communication with theoutside system in the manner already described.

Of course, after the operator has pulled out the switch actuating rod 66' of the acoustical coupling device C, the energizing circuit of the buzzer I23 is interrupted by the separation of the spring contacts 290 and 292 of the control switch I0,-whereupon the' buzzer ceases to function. The operator then restores the French telephone instrument F to its normal position upon the cradle of the main subscribers telephone set T.

Thereupon, the added weight of the instrument F depresses the floating platform of the subbase (shown in Fig. 1) and eifects a disengagement of the spring contacts 20' and 24 whereby the amplifier 90' is cut off from the source of power. At the same time visible signal device 36 also becomes inoperative.

The combined inter-outer telephone system is then in readiness for further use, either in interofflc'e communication or communication by means of an acoustical connection with the outside system.

While I have described in detail the operation of my improved inter-outer telephone system, as illustrated in Figs. 1 and 4, in connection with receiving a call from the outside system for a party at one of the branch stations of the interoflice system, it will be understood without further explanation that the call may originate from any of the inter-office branch stations. Moreover, the operator may at any time call any of the branch stations and any of the branch stations may call the operator.

Referring now to Fig. 5 of the drawings, 1 have illustrated diagrammatically a modification of my invention which may be utilized in connection with inter-outer telephone systems of various types, including those describedwith respect 1 to Fig. 1 and Fig. 4, and which embodies adirect current battery-operatedelectronic amplifier in lieu of an alternating current type of amplifier previously referred to.

Direct current battery-operated amplifiers are known in the art, and are generally similar in construction and operation to alternating current amplifiers, with the exception that they include a so-called A" battery, a B battery and a C battery for supplying the necessary energy instead of being connected to a source of alternating ordirect current energy. The A battery supplies the energy for heating up the vacuum tubes of the amplifier to bring them to operative condition, and B and C batteries automatically become operative to perform their usual functions when the resistance of the vacuum tubes is overcome through suitable heating thereof by the A battery. With such a battery operated type of electronic amplifier, it is particularly important to utilize a minimum of energy from theauxiliary A, B and C batteries and, therefore, the amplifier should be energized only when actually in use. The feature of my invention involving the immediate and automatic energization of the amplifier upon removing the French telephone instrument from the-cradle of the subscribers telephone set, is-therefore of prime importance when control purposes, and restrict the A battery as far as possible to merely supply the energizing current for the amplifier.

Referring specifically to Fig. 5, a regulatable direct current amplifier 90 constituting a part of my acoustical coupling device 0, is provided with an A battery 406 for supplying the energizing current to preliminarily heat the amplifier up to operating condition, and a B battery,

408 and a C battery-M0, operating in the usual manner which need not be described. The A battery 406 is connected to the amplifier 90 by means of an electromagnetically operated relay or switch 4l2 which embodies an electromagnet 4H and a pivotally mounted armature switch arm 6 carrying an electrical contact 8, which cooperates with a stationary contact 420 in the usual manner. The armature M6 is normally held in open position by a spring 422. However, when the control circuit from the source of energy marked Power 'is completed through contacts 20 and 24 by the removal of the French telephone instrument F from the cradle of the subscriber's telephone set T in the manner previously setforth, the electromagnet M4 is energized and draws its armature 6 into position to effect a cooperative engagement between the contacts 8 and 420. In this way an energizing circuit for the amplifier 90 is completed from one side of the A battery 406, through conductor 424, cooperating contacts 420 and 4| 8 of the electromagnetioally operated switch M2, and thence through the armature switch arm 4| 6 and conductor 426 to one terminal 428 of the amplifier, the other terminal 428 of which is already connected by conductor 430 to the other side of the A battery 406.

The direct current battery-operated amplifier 90 is thereby connected to its A battery 406 as soon as the French telephone instrument is removed from its cradle, and the warming-up period of the amplifier tubes is thus promptly initiated.

Of course, at the same time that the French telephone instrument is picked up and coopera tive engagement of contacts 20 and 24 is established, a suitable signal device 36 and a timing device 42 are also connected across the source of power and become operative, as will be readily understood from the previous description. These auxiliary devices, as well as the 'electro-magnetically operated switch or relay 2, are preferably connected to the usual power source in order to relieve the A battery 406 of unnecessary service..

Without further description, it will be understood that aside from the modified operation just set forth, the inter-outer telephone system of my invention operates in the manner previously explained, whereby an outside telephone call may be received acoustically by a party at any branch station. Obviously, when the conversation has terminated and the French telephone instrument has been restored to its cradle, the contacts 20 and 24 are disengaged and the power cut off from the signal device 36 the timing device 42 and the electromagnet 4 of the relay switch 4l2. Thus, the energizing circuit of the amplifier 90 is interrupted by the separation of contacts 4| 8 and 420, and the A battery 406 is thus disconnected from service.

Subsequently, the B battery 406 and C battery .connections, as well as steps of operation, it should be understood that many modifications may be made therein without departing from the spirit and scope of my invention. Therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim: 1. In a telephone system, the combination of a subscriber's telephone set including a supporting base and a removable telephone instrument normally resting thereon, an electronic amplifier, means for acoustically coupling said instrument to said amplifier and means upon which the telephone set is adapted to rest and operatively dependent upon the weight thereof for automatically energizing said amplifier when the telephone instrument is removed from its supporting base.

2. In a. telephone system, the combination of a subscrlbers telephone set including a supporting base and a removable telephone instrument normally resting thereon, a timing device of the electric clock type for progressively indicating the passage of time and means upon which the telephone set is adapted to rest and operatively dependent upon the weight thereof for automatically initiating the operation of said timing device' when the telephone instrument is removed from its supporting base for purposes of telephonic communication to progressively indicate the length of time of said telephonic communication.

3. A system of telephonic communication com prising in combination a public telephone system including a telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent inter-oflice telephone system including an electronic amplifier for amplifying messages received acoustically by the inter-oflice system, means for effecting an acoustical coupling between said inter-ofilce telephone system and public telephone system and means associated with said public telephone set for automatically energizing said amplifier upon removing saidtelephone instrument from its supporting base.

4. A system of telephonic communication comprising in combination a public telephone system including a telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent inter-ofllce telephone system, an electronic amplifier for amplifying messages received acoustically by the inter-oflice system, means for efiecting an acoustical coupling between said public and said inter-ofiice telephone systems, a sub-base including a spring-supported floating platform upon which the public telephone set is adapted to rest, and means including a plurality of relatively movable electrical contacts operatively associated with said floating platform and adapted for electrical engagement when the telephone instrument is removed from its base for automatically connecting the amplifier to a source of power.

5.. A system of telephonic communication comprising in combination a public telephone system including a telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent inter-oflice telephone system includinga battery-operated electronic amplifier including an associated with the public telephone set for automatlcally connecting the A battery to the electronic amplifier upon the removal of the telephone instrument from its supporting base.

6. A system of telephonic communication comprising in combination a public telephone system including a. telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent inter-oflice telephone system, a battery-operated electronic amplifier including an A battery for heating the amplifier to operative condition, means for efiecting anacoustical coupling. be-

a tween said public and said inter-oflice telephone systems, and means associated with the public 1 telephone set and'including an electromagnetically operated relay switch for automatically .connecting the A battery to the electronic amplifier upon the removal of the telephone instrument from its supporting base.

'7. A system of telephonic communication comprising in combination a public telephone system including a telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent interoflice telephone system, means for effecting an acoustical coupling between said public and said,

inter-oflice telephone systems, a timing device of the electric clock type and means associated with said public telephone set and dependent upon the weight thereof for initiating the operation of said timing device upon the removal of the telephone instrument from its supporting base.

8. A system-of telephonic communication comprisingin combination a public telephone system including a telephone set having a supporting base and a removable telephone instrument normally resting thereon, an electrically independent interofilce telephone system, means for effecting an acoustical coupling between said public and said inter-oflice telephone systems, a timing device of the electric clock type, a spring-supported floating platform upon which the telephone set is adapted to rest and electrical means operatively associated with said floating platform for initiating the operation of said timing deviceupon the removal of the telephone instrument from its supporting base. 7

9. A system of telephonic communication comprising in combination, a public telephone system including a telephone instrument, aninter-oflice telephone system comprising independently operable transmitting and receiving circuits, said transmitting circuit including a transmitter ata branch station and a loud-speaker at an operators station, and said receiving circuit including a receiver at said branch station and a transmitter at said operator's station, an electronic amplifier in one of said circuits, switching means located at said branch station and normally held in inoperative open position by the weight of said receiver at the branch station but actuated into operative closed position when said receiver is picked up for conversation to connect said transmitting and said receiving circuits into operative relation, and means for eifecting an acoustical said inter-ofiice telephone system.

station, said transmitting circuit including a transmitter'at the branch station and a loudspeaker at the operators station, and said receiving circuit including a receiver at said branch station, a transmitter and an amplifier at said operators station, switching means located at the branch station and normally held in inoperative open position by the weight of the receiver at the branch station, but actuated into J operative closed position when the receiver is picked up, for connecting said transmitting and receiving circuits into independent operative relation, and means located at the operators station for effecting an acoustical coupling between said public telephone instrument and said interoflice system. i

11. A system of telephonic communication comprising in combination a public telephone system having a telephone instrument, an inter-ofiice telephone system having operably independent transmitting and receiving circuits adapted to be set up between an operators station and a branch station, said transmitting circuit including a transmitter at the branch station and a loud-speaker at the operators" station, and said receiving circuit including a receiver at said branch station, a transmitter and an amplifier at said operators station, switching means located at the branch station and normally held in inoperative open position by the weight of the receiver at the branch station but actuated into operative closed position when the receiver is picked up for connecting said transmitting and receiving circuits into independent operative relation, means located at the operators station for effecting an acoustical coupling betweensaid public telephone instrument and said interofiice system, a signal devicev at the operators station having a normally open energizing circuit during an outside telephone conversation, and control means including a circuit through said branch station switching means adapted to be rendered operable only when the outside telephone conversation has terminated and the branch station receiver is restored to its normal inoperative positionto effect the completion of said signal energizing circuit and operate said signal device.

12. A system of-telephonic communication comprising in combination a public telephone system having a telephone instrument, an inter-oflice telephone system having operably independent transmitting and receiving circuits adapted to be set up between an operators station and a branch station, means locatedat said operators station tem'having a telephone instrument, an interofiice telephone system having operably independent transmitting and receiving circuits adapted to be set up between an operator's station and a branch station, an acoustical coupling device at said operators station adapted to receive and support the public telephone instrument in efilcient acoustical relation with the operably independent transmitting and receiving circuits of said inter-ofllce system, a switching device at said operator's station arranged to be actuated by the operator into operative position when the public telephone instrument is placed in acoustical relation with said coupling device, a switching device at said branch station biased to its operative closed position but held in inoperative open position by the weight of the branch station receiver when hung up, a signal device at said operators station and control means cooperatively associated with both of said switching devices and said signal device for eflecting the operation of said signal device while said coupling device is in operative position and when said branch station receiver is hung up after the termination of a telephone conversation.

14. A system of telephonic communication comprising in combination a public telephone system including a telephone instrument, an inter-office telephone system comprising a two-wire one-way receiving circuit including a receiver at a branch station and a transmitter and an amplifier at an operators station, a separate and independent two-wire one-way transmitting circuit including a transmitter at the branchstation and a receiver at the operator's station, and a switching device at the branch station normally held in inoperative open position by the weight of the receiver at said station but actuated into operative closed position when relieved of the weight of the receiver, said switching device being arranged in said separate two-wire one-way transmitting and receiving circuits to automatically effect the establishment of said circuits when the branch station receiver is picked up for use, and means for efiecting an acoustical coupling between said telephone instrument and said interofiice system.

15. A system of telephonic communication, comprising in combination a public telephone system including a telephone instrument, an inter-ofiice telephone system comprising operably independent transmitting and receiving circuits including a three-wire circuit, one of which is a common return for both the transmitting and the receiving circuits, the receiving circuit including a receiver at a branch station and an amplifier and a transmitter at the operators station, the transmitting circuit including a transmitter at the branch station and a receiver, at

the operators station, a battery included in the common return of said transmitting and receiving circuits, and a switching device at the branch station for establishing said transmitting and receiving circuits when the receiver at the branch station is picked up for use, said switching device being held in inoperative open position by the weight of the receiver when not in use.

16. An inter-ofllce telephone system comprising a transmitting circuit including a transmitter at a receiving station and a receiver at an operators station, a receiving circuit including a receiver at the branch station and a transmitter at the operators station, a phonographic soundrecording device controllable at the operators station and including a loud-speaker operatively associated with said recording device, means including circuit connections and a switching device at the operators station for operatively con necting the transmitter at the operator's station with either the receiver at the branch station or the loud-speaker associated with said sound-recording device whereby a message can be received at the branch station or be recorded on the soundrecording device, and means for acoustically picking 'up such message from the loud-speaker associated with said sound-recording device and transmitting it to the receiver at ,the branch station while the message is being recorded by the sound-recording device.

17. A system for recording telephonic messages comprising a phonographic sound-recording device, a loud-speaker acoustically associated therewith, a transmitter constituting a part of a transmitting circuit including said loud-speaker, means for controlling the operation of said soundrecording device to record messages originating in said transmitter and delivered to said loudspeaker, a pick-up microphone located adjacent switching device at each of the branch stations for establishing independently operable receiving and transmitting circuits between the operators station and the branch stations, said switching means at the branch stations being normally held in inoperative open position by the weight of the respective receivers at said stations but actuated into operative closed positions when the receivers are picked up for use, a plurality of series-connected electromagnetically operated latching devices located at the respective branch stations and adapted to be actuated into locking engagement with the respective switching devices at said branch stations when the receiver at one of said branch stations is picked up for use, and means at the respective branch stations operatively asso ciated with the respective electromagnetically operated latching means at said branch stations for indicating at all of said branch stations, except the one in use, that the inter-oflice telephone system is being used.

'19. An inter-ofllce telephone system for interconnecting a plurality of branch stations with a main or operators station, comprising a transmitter and a receiver at the operators station and each of the branch stations, means including a switching device at each of the branch stations for establishing independently operable receiving and transmitting circuits between the operators station and the branch stations, said switching means at the branch stations being normally held in inoperative open position by the weight of the respective receivers at said stations but actuated into operative closed'positions when the receivers are picked up for use, and electromagnetically operated meansrendered operative when the receiverat any of the branch stations is picked up for use for preventing the operation of the switching devices at all the other branch stations until the receiver in use is restored to its normal position. 4

20. An inter-oflice telephonesystem for. interconnecting a plurality of branch stations with a main or operators station, comprising a transmitter and a receiver at the operators station and each of the branch stations, means including a aovaoae J switching device at each of the branch stations for establishing independently operable receiving and transmitting circuits between the operator's station and the branch stations, said switching phone instrument, an inter-oflice telephone system electrically independent thereof and having a transmitting circuit including a transmitter at a branch station and a loud-speaker at the operators station, an independently'operable receiving circuit including a receiver at the branch station and a transmitter at the operators station, a. switching device at said branch station for setting up said transmitting and receiving circuits when the receiver at said branch station is picked'up for use, an acoustical coupling device at the operators station including said loud-speaker, an auxiliary transmitter, and an amplifier in circuit therewith, for effecting an acoustical coupling between the telephone instrument of the public telephone system and said inter-ofllce system, and switching meansat the operators station adapted to be actuated when the acoustic coupling is effected for disconnecting the first-mentioned transmitter at the operators station from said receiving circuit while establishing a receiving circuit including the auxiliary transmitter and the amplifier at the operators station and the receiver at the branch station.

22. In an acoustic coupling device for acoustically connecting a French telephone instrument of a public telephone system with a separate and independent inter-oflice telephone system, the combination of a cabinet having a vertically inclined panel provided with a pair of vertically disposed openings spaced to register-with the fixedly spaced transmitter and receiver of the French telephone instrument, a microphone and a loud speaker mounted within the cabinetimmediately behind the upper and lower panel openings respectively, a semi-circular outwardly projecting flange positioned immediately below the upper panel opening to receive the receiver end of the French telephone instrument and support said instrument in efficient acoustical relation with said microphone and loud-speaker, a control switch mounted within the cabinet and a switchactuating rod associated therewith and projecting.

outwardly through said panel intermediate said panel openings with its outer end in position to engage the hand grip of the French telephone instrument and prevent it from being placedin ei'licient acoustical relation with said microphone andloud-speaker until said switch-actuating rod is depressed to effect the actuation of said control switch.

23. A system of telephonic communication, comprising in combination a public telephone system including a supporting base and a removable telephone instrument normally resting thereon, an electrically independent inter-oiiice telephone system having an operators station and a branch station adapted to be interconnected by independently operable receiving and transmitting'telephone circuits, each circuit including a telephone receiver and a telephone transmitter, both the public and the independent inter-dflice systems being normally capable of independent conventional use but also adapted to be interconnected acoustically when the operator manually places the telephone instrument of the public telephone system in acoustical relation wlth'the receiver and the transmitter located at the operators station or the inter-'ofllce system, and switching means located atthe branch station oi the inter-oiiice system and normally held in inoperative position for establishing the indevpendently operable transmitting and receiving circuits when the receiver at said branch station is picked up for use. 24. A system of telephonic communication comprising in combination a public telephone system having a telephone instrument, an interofllce telephone system having operably' independent transmitting and receiving circuits adapted to be set upbetween an operators station and a branch station, said transmitting circuit including a transmitter at the branch station and a loud-speaker at the operators station, and said receiving circuit including a receiver at said branch station, a transmitter and an amplifier at said operators station, switching means located at the branch station and normally held in inoperative open position by the weight of the receiver at the branch station but actuated into operative closed position when the receiver is picked up for connecting said transmitting and receiving circuits into independent operative relation, means located at the operators station for effecting an acoustical coupling between said public telephone instrument and said inter-ofllce system, and signalimeans atthe operators station and controllable by the switching means at said branch station for warning the operator' when the receiver at the branch station has been restored to its normal inoperative position after an inter-outer telephone connection has been interrupted at said branch station.

25. A system of telephonic communication comprising in combination, a telephone system having a loud-speaker adapted to receive telephonic messages, a phonographic sound-recording device with which said loud-speaker is acoustically associated for recording the telephonic messages received by said loud-speaker, means disposed in acoustical relation to said loud-speaker for picking up the telephonic messages from said loud-speaker and relaying them to a distant telephone receiver while said messages are being recorded.

26. An inter-ofiice telephone system adapted to interconnect a plurality of branch stations with a main or operators station, means at each branch-station for establishing telephone connections between such branch station and the operators station and automatic means interf locking all of said branch stations for preventing the operation of all but one of said branch stations when said one of said branch stations is I in use.

2'7. An inter-oflice telephone system adapted to interconnect a plurality of branchstations' with "a main or operators station, means at each branch station for establishing telephoneconinterconnect a plurality of branch stations with a main or operator's station, means at each branch station for establishing telephone connections between such branch station and the operators station and automatic means interlocking all of said branch stations for preventing the operation of and eflfecting a signal at all but one of said branch stations when said one of said branch stations is in use.

29. In an acoustical coupling device for acoustically connecting a French telephone instrument of a public telephone system with a separate and electrically independent inter-oflice telephone system, the combination of a cabinet having a 15 vertically inclined panel provided with a pair of vertically disposed openings spaced to register with the fixedly spaced transmitter and receiver of the French telephone instrument, a microphone Hid a loud-speaker mounted within the cabinet in operative proximity to said upper and lower panel openings, means associated with said 

